| COST 639 - WG 3 |  |
European forest soils are monitored in a harmonized way (ICP Forest, Forest Focus), but for other forms of land-use the harmonization is less advanced. Peatlands are fundamentally different from mineral soils and require a specific monitoring method. The loss in C stocks is difficult to measure and less relevant in relation to emissions of CH4 and N2O. We foresee in this respect collaboration between WG1 (peatlands) and WG3. The detection of small changes in soil C and N stocks requires great sampling efforts. We will recommend specific sampling schemes with stratified sampling for the detection of relatively subtle (compared to the stock) soil C and N stock changes with a large impact on greenhouse gas budgets (sampling in hot spots / WG 1).
We will evaluate already existing soil C and N models (CO2Fix, Century, DNDC and others) for the verification of stock changes. As an interaction between WG1 and WG3, the representation of ecosystem disturbance in a model framework is sought. It is crucial to show where models are currently failing and to improve the interface with experts in field research and modelling. The assessment of stock changes requires a baseline for comparison. The present baseline is, arbitrarily, the pool size in the year 1990. We will attempt to establish a more meaningful baseline based on land-use, land-use history, and site properties.
Pool sizes for soil C and N are calculated from several input values. Each has an error that propagates. On top of the variability at the spot, the small- and medium-scale spatial variation has to be considered. We will clarify how the variability of C and N pools can be comprehensively assessed under different situations of data availabilities. We will address the size of soil C and N stock changes that are theoretically required in order to be relevant for GHG reporting purposes. An error budget for undisturbed forests has been established in the project CarboInvent (FP 5) and the rules of accounting for errors are described in the Good Practice Guidance of the IPCC. Based on data that are available from WG1, error budgets of C and N pool changes will be presented for peatlands.
An additional task of WG3 is to develop a risk assessment for GHG emissions from ecosystems. Signatory countries of the Kyoto Protocol are including the sink strength of terrestrial ecosystems in their GHG budgets. Ecology teaches that ecosystems have an inherent stability, a typical life span, and have a certain probability of being subject to disturbances. A risk assessment needs to express the probability of ecosystem disturbances based on the knowledge of the past course of events and with hindsight to the effects of future changes (both with respect to land use and to climate). Within the WG, the data requirements for a risk assessment will be collected and compared with the availability of useful statistics in Europe (spatial / temporal resolution of records of wind damages, insect damages etc).